Treatment for alzheimer&#39;s disease and related conditions

ABSTRACT

There is disclosed the combination of a growth hormone secretagogue and at least one agent which modifies the production or processing of Aβ in the brain, said at least one agent being selected from: (a) compounds which inhibit the secretion of Aβ; (b) compounds which selectively inhibit the secretion of the 1-42 isoform of Aβ; (c) compounds which inhibit the aggregation of Aβ; and (d) antibodies which selectively bind to Aβ; for use in treatment or prevention of a disease associated with deposition of Aβ in the brain.

This invention relates to the use of methods and materials fortherapeutic treatment of the human body. In particular, it providesmethods of treating diseases associated with the deposition of β-amyloidin the brain, such as Alzheimer's disease, or of preventing or delayingthe onset of dementia associated with such diseases.

Alzheimer's disease (AD) is the most prevalent form of dementia Itsdiagnosis is described in the Diagnostic and Statistical Manual ofMental Disorders, 4^(th) ed., published by the American PsychiatricAssociation (DSM-IV). It is a neurodegenerative disorder, clinicallycharacterized by progressive loss of memory and general cognitivefunction, and pathologically characterized by the deposition ofextracellular proteinaceous plaques in the cortical and associativebrain regions of sufferers. These plaques mainly comprise fibrillaraggregates of β-amyloid peptide (Aβ). Aβ is formed from amyloidprecursor protein (APP) via separate intracellular proteolytic eventsinvolving the enzymes β-secretase and γ-secretase. Variability in thesite of the proteolysis mediated by γ-secretase results in Aβ of varyingchain length, e.g. Aβ(1-38), Aβ(1-40) and Aβ(142). N-terminaltruncations such as Aβ(4-42) are also found in the brain, possibly as aresult of variability in the site of proteolysis mediated byβ-secretase. For the sake of convenience, expressions such as “Aβ(140)”and “Aβ(1-42)” as used herein are inclusive of such N-terminal truncatedvariants. After secretion into the extracellular medium, Aβ formsinitially-soluble aggregates which are widely believed to be the keyneurotoxic agents in AD (see Gong et al, PNAS, 100 (2003), 10417-22),and which ultimately result in the insoluble deposits and dense neuriticplaques which are the pathological characteristics of AD.

Other dementing conditions associated with deposition of Aβ in the braininclude cerebral amyloid angiopathy, multi-infarct dementia, dementiapugilistica and Down syndrome.

Various interventions in the plaque-forming process have been proposedas therapeutic treatments for AD (see, for example, Hardy and Selkoe,Science, 297 (2002), 353-6). One such method of treatment that has beenproposed is that of blocking or attenuating the production of Aβ, forexample by inhibition of β- or γ-secretase. Compounds which inhibitγ-secretase are disclosed in WO 01/53255, WO 01/66564, WO 01/70677, WO01/90084, WO 01/77144, WO 02/30912, WO 02/36555, WO 02/081435, WO02/081433, WO 03/018543, WO 03/013506, WO 03/013527, WO 03/014075, WO03/093252, WO 2004/031137, WO 2004/031138, WO 2004/031139, WO2004/039800 and WO 2004/039370. Compounds which inhibit β-secretase aredisclosed in WO 03/037325, WO 03/030886, WO 03/006013, WO 03/006021, WO03/006423, WO 03/006453, WO 02/002122, WO 01/70672, WO 02/02505, WO02/02506, WO 02/02512, WO 02/02520, WO 02/098849 and WO 02/100820. Othercompounds which inhibit the formation or release of Aβ include thosedisclosed in WO 98/28268, WO 02/47671, WO 99/67221, WO 01/34639, WO01/34571, WO 00/07995, WO 00/38618, WO 01/92235, WO 0177086, WO01/74784, WO 01/74796, WO 01/74783, WO 01/60826, WO 01/19797, WO01/27108, WO 01/27091, WO 00/50391, WO 02/057252, US 2002/0025955 andUS2002/0022621.

It has also been reported that inhibition of glycogen synthase kinase-3(GSK-3), in particular inhibition of GSK-3α, can block the production ofAβ (see Phiel et al, Nature, 423 (2003), 435-9).

Another such method of treatment that has been proposed is that ofmodulation of the action of γ-secretase so as to selectively attenuatethe production of Aβ (142). This results in preferential secretion ofthe shorter chain isoforms of Aβ, which are believed to have a reducedpropensity for self-aggregation and plaque formation, and hence are moreeasily cleared from the brain, and/or are less neurotoxic. Compoundsshowing this effect include certain non-steroidal antiinflammatory drugs(NSAIDs) and their analogues (see WO 01/78721 and US 2002/0128319).Compounds which modulate the activity of PPARα and/or PPARδ are alsoreported to have the effect of lowering Aβ 1-42 (WO 02/100836). NSAIDderivatives capable of releasing nitric oxide have been reported to showimproved anti-neuroinflammatory effects and/or to reduce intracerebralAβ deposition in animal models (WO 02/092072; Jantzen et al, J.Neuroscience, 22 (2002), 226-54).

Another such method of treatment that has been proposed is that ofadministering a compound which blocks the aggregation of Aβ. Compoundshaving this property include chelating agents such as clioquinol (Gourasand Beal, Neuron, 30 (2001), 641-2) and the compounds disclosed in WO99/16741, in particular that known as DP-109 (Kalendarev et al, J.Pharm. Biomed. Anal., 24 (2001), 967-75). Other inhibitors of Aβaggregation include the compounds disclosed in WO 96/28471, WO 98/08868and WO 00/052048, including the compound known as Apan™ (Praecis), WO00/064420, WO 03/017994, WO 99/59571 and the compound known as Alzhemed™(Neurochem), WO 00/149281 and the compositions known as PTI-777 andPTI-00703 (ProteoTech), WO 96/39834, WO 01/83425, WO 01/55093, WO00/76988, WO 00/76987, WO 00/76969, WO 00/76489, WO 97/26919, WO97/16194, and WO 97/16191.

Another such method of treatment that has been proposed is that ofadministering an antibody which selectively binds to Aβ. Such antibodiesmay be brain-penetrant and capable of binding to insoluble Aβ, asdescribed in WO 99/60024 and WO 00/72880 for example. Alternatively,such antibodies may be capable of sequestering soluble Aβ frombiological fluids, without necessarily being brain-penetrant. It isbelieved that in these circumstances the removal of unbound Aβ from theserum increases the relevant concentration gradient between brain andserum, causing an efflux of Aβ from the brain to the serum. Thisapproach is described in WO 03/016466, WO 03/016467, WO 03/015691 and WO01/62801. The use of antibodies specific to Aβ-derived diffusableligands (ADDLS) has also been proposed (WO 2004/031400).

Growth hormone has been proposed for use in treatment of AD. Thus, U.S.Pat. No. 4,902,680 advocates the administration of growth hormone topatients in the advanced stages of AD, while WO 00/13650 discloses thatincreased levels of growth hormone in the brain provide aneuroprotective effect, and in particular can rescue neurons that wouldotherwise die as a result of an insult such as that associated with aneurodegenerative disease such as AD. The injection of growth hormoneinto the brain is contemplated.

Growth hormone secretagogues (GHSs) are compounds which, whenadministered to an animal (such as a human), stimulate or increase therelease of endogenous growth hormone in the animal. Their mode of actionand clinical utilities are reviewed by Ankersen et al, Drug DiscoveryToday, 4 (1999), 497-506; Casanueva and Dieguez, TEM, 10 (1999), 30-8;Smith et al, ibid., 10 (1999), 128-35; Betancourt and Smith, J.Anti-Aging Med., 5 (2002), 63-72; and Ghigo et al, ibid., 5 (2002),345-56, but there is no mention of treating AD or any otherneurodegenerative condition. Patents and patent applications disclosingcompounds which are GHSs include U.S. Pat. No. 5,767,124, U.S. Pat. No.5,536,716, WO 94/13696, EP 0615977B, U.S. Pat. No. 5,578,593; WO01/04119, WO 98/25897, WO 98/10653, WO 97/36873, WO 97/34604, WO97/15574, WO 97/11697, WO 96/32943, WO 96/13265, WO 96/02530, WO95/34311, WO 95/14666, WO 95/13069, WO 94/19367, WO 94/05634 and WO92/16524 (all assigned to Merck & Co., Inc.); EP 1002802A, EP 0995748A,WO 98/58948, WO 98/58947 and WO 97/24369 (all assigned to Pfizer Inc.);WO 01/34593, WO 00/26252, WO 00/01726, WO 99/64456, WO 99/58501, WO99/36431, WO 98/58950, WO 98/08492, WO 98/03473, WO 97/40071, WO97/40023, WO 97/23508, WO 97/00894, WO 96/24587, WO 96/24580, WO96/22997, WO 95/17423 and WO 95/17422 (all assigned to Novo NordiskA/S); WO 96/15148 (Genentech Inc.); WO 97/22620 (Deghenghi); WO02/32888, WO 02/32878, WO 00/49037, WO 00/10565 and WO 99/08699 (allassigned to Eli Lilly and Co.); WO 02/057241 and WO 02/056873 (bothassigned to Bayer Corp.); and WO 01/85695, WO 00/54729 and WO 00/24398(all assigned to Bristol-Myers Squibb Co.). The compounds arerecommended for use in promoting the growth of food animals, and inhumans for treating physiological or medical conditions characterised bya deficiency in growth hormone secretion, and medical conditions whichare improved by the anabolic effects of growth hormone. In some of theabove-listed disclosures, the list of treatable conditions includes AD.

The compound disclosed in the aforementioned U.S. Pat. No. 5,767,124 hasbeen the subject of a number of clinical trials in therapeutic fieldsunrelated to AD (see, for example, Murphy et al, J. Bone Miner. Res.,14, (1999), 1182-8; Chapman et al, J. Clinical Endocrinology andMetabolism, 81, (1996), 4249-57; ibid., 82, (1997), 3455-63; andSvensson et al, ibid., 83, (1998), 362-9).

According to the invention, there is provided the combination of agrowth hormone secretagogue and at least one agent which modifies theproduction or processing of Aβ in the brain, said at least one agentbeing selected from:

(a) compounds which inhibit the secretion of Aβ;

(b) compounds which selectively inhibit the secretion of the 1-42isoform of Aβ;

(c) compounds which inhibit the aggregation of Aβ; and

(d) antibodies which selectively bind to Aβ;

for use in treatment or prevention of a disease associated withdeposition of Aβ in the brain.

Also according to the invention, there is provided a method of treatmentor prevention of a disease associated with deposition of Aβ in the braincomprising administering to a subject in need thereof a therapeuticallyeffective amount of a growth hormone secretagogue (GHS) in combinationwith a therapeutically effective amount of at least one agent whichmodifies the production or processing of Aβ in the brain, said at leastone agent being selected from:

(a) compounds which inhibit the secretion of Aβ;

(b) compounds which selectively inhibit the secretion of the 1-42isoform of Aβ;

(c) compounds which inhibit the aggregation of Aβ; and

(d) antibodies which selectively bind to Aβ.

Said disease is typically Alzheimer's disease, cerebral amyloidangiopathy, multi-infarct dementia, dementia pugilistica or Downsyndrome, preferably Alzheimer's disease.

The invention further provides a method of treating, preventing ordelaying the onset of dementia associated with Alzheimer's disease,cerebral amyloid angiopathy, multi-infarct dementia, dementia puglisticaor Down syndrome comprising administering to a patient in need thereof atherapeutically effective amount of a growth hormone secretagogue incombination with a therapeutically effective amount of at least oneagent as defined above which modifies the production or processing of Aβin the brain.

As used herein, the expression “in combination with” requires thattherapeutically effective amounts of both a GHS and an agent whichmodifies the production or processing of AP in the brain (hereinaftertermed an “amyloid modifier”) are administered to the subject, butplaces no restriction on the manner in which this is achieved. Thus, thetwo species may be combined in a single dosage form for simultaneousadministration to the subject, or may be provided in separate dosageforms for simultaneous or sequential administration to the subject.Sequential administration may be close in time or remote in time, e.g.one species administered in the morning and the other in the evening.The separate species may be administered at the same frequency or atdifferent frequencies, e.g. one species once a day and the other two ormore times a day. The separate species may be administered by the sameroute or by different routes, e.g. one species orally and the otherparenterally, although oral administration of both species is preferred,where possible. When the amyloid modifier is an antibody, it willtypically be administered parenterally and separately from the GHS.

According to a further aspect of the invention there is provided apharmaceutical composition comprising, in a pharmaceutically acceptablecarrier, a growth hormone secretagogue and an amyloid modifier selectedfrom:

(a) compounds which inhibit the secretion of Aβ;

(b) compounds which selectively inhibit the secretion of the 1-42isoform of Aβ; and

(c) compounds which inhibit the aggregation of Aβ.

The invention further provides the use, for the manufacture of amedicament for treatment or prevention of a disease associated withdeposition of AP in the brain, of a growth hormone secretagogue and anamyloid modifier selected from:

(a) compounds which inhibit the secretion of Aβ;

(b) compounds which selectively inhibit the secretion of the 1-42isoform of Aβ;

(c) compounds which inhibit the aggregation of Aβ.

Said disease is typically Alzheimer's disease, cerebral amyloidangiopathy, multi-infarct dementia, dementia pugilistica or Downsyndrome, preferably Alzheimer's disease.

The GHS and amyloid modifier act synergistically in reducing theaccumulation of Aβ in the brain. Therefore, in a further aspect theinvention provides a method for retarding, arresting or preventing theaccumulation of Aβ in the brain comprising administering to a subject inneed thereof a therapeutically effective amount of a growth hormonesecretagogue in combination with a therapeutically effective amount ofan amyloid modifier as defined above.

Because of the aforementioned synergistic interaction, it is possible toobtain a beneficial therapeutic effect from the administration of dosesof the compounds in question that are smaller than would typically beemployed for individual administration of the same compounds. Forexample, a compound which inhibits secretion of Aβ (such as aγ-secretase inhibitor) may be dosed at a level which does not completelysuppress the production of Aβ, yet still exert a therapeutic effectcomparable to full suppression thereof, as a result of co-administrationof the GHS. This has the potential to prevent side-effects that mightarise from the suppression of other activities, unconnected with Aβproduction, such as the notch signalling process.

Clearance of Aβ from the brain following administration of the relevantcompounds may be evidenced by an increase in the level of soluble Aβ inthe cerebrospinal fluid and/or the plasma. Alternatively (oradditionally), imaging techniques such as magnetic resonance imaging,positron emission tomography, single photon emission computed tomographyand multiphoton microscopy may be employed to monitor the extent of Aβdeposition in the brain (see, for example, Bacskai et al., J. Cereb.Blood Flow Metab., 22 (2002), 1035-41).

In one embodiment of the invention, the GHS and amyloid modifier areadministered to a patient suffering from AD, cerebral amyloidangiopathy, multi-infarct dementia, dementia pugilistica or Downsyndrome, preferably AD.

In an alternative embodiment of the invention, the GHS and amyloidmodifier are administered to a patient suffering from mild cognitiveimpairment or age-related cognitive decline. A favourable outcome ofsuch treatment is prevention or delay of the onset of AD. Age-relatedcognitive decline and mild cognitive impairment (MCI) are conditions inwhich a memory deficit is present, but other diagnostic criteria fordementia are absent (Santacruz and Swagerty, American Family Physician,63 (2001), 703-13). (See also “The ICD-10 Classification of Mental andBehavioural Disorders”, Geneva: World Health Organisation, 1992, 64-5).As used herein, “age-related cognitive decline” implies a decline of atleast six months' duration in at least one of: memory and learning;attention and concentration; thinking; language; and visuospatialfunctioning and a score of more than one standard deviation below thenorm on standardized neuropsychologic testing such as the MMSE. Inparticular, there may be a progressive decline in memory. In the moresevere condition MCI, the degree of memory impairment is outside therange considered normal for the age of the patient but AD is notpresent. The differential diagnosis of MCI and mild AD is described byPetersen et al., Arch. Neurol., 56 (1999), 303-8. Further information onthe differential diagnosis of MCI is provided by Knopman et al, MayoClinic Proceedings, 78 (2003), 1290-1308. In a study of elderlysubjects, Tuokko et al (Arch, Neurol., 60 (2003) 577-82) found thatthose exhibiting MCI at the outset had a three-fold increased risk ofdeveloping dementia within 5 years.

Grundman et al (J. Mol. Neurosci., 19 (2002), 23-28) report that lowerbaseline hippocampal volume in MCI patients is a prognostic indicatorfor subsequent AD. Similarly, Andreasen et al (Acta Neurol. Scand, 107(2003) 47-51) report that high CSF levels of total tau, high CSF levelsof phospho-tau and lowered CSF levels of Aβ42 are all associated withincreased risk of progression from MCI to AD.

Within this embodiment, the GHS and amyloid modifier are advantageouslyadministered to patients who suffer impaired memory function but do notexhibit symptoms of dementia. Such impairment of memory functiontypically is not attributable to systemic or cerebral disease, such asstroke or metabolic disorders caused by pituitary dysfunction. Suchpatients may be in particular people aged 55 or over, especially peopleaged 60 or over, and preferably people aged 65 or over. Such patientsmay have normal patterns and levels of growth hormone secretion fortheir age. However, such patients may possess one or more additionalrisk factors for developing Alzheimer's disease. Such factors include afamily history of the disease; a genetic predisposition to the disease;elevated serum cholesterol; and adult-onset diabetes mellitus.

In a particular embodiment of the invention, GHS and amyloid modifierare administered to a patient suffering from age-related cognitivedecline or MCI who additionally possesses one or more risk factors fordeveloping AD selected from: a family history of the disease; a geneticpredisposition to the disease; elevated serum cholesterol; adult-onsetdiabetes mellitus; elevated baseline hippocampal volume; elevated CSFlevels of total tau; elevated CSF levels of phospho-tau; and lowered CSFlevels of Aβ(1-42).

A genetic predisposition (especially towards early onset AD) can arisefrom point mutations in one or more of a number of genes, including theAPP, presenilin-1 and presenilin-2 genes. Also, subjects who arehomozygous for the ε4 isoform of the apolipoprotein E gene are atgreater risk of developing AD.

The patient's degree of cognitive decline or impairment isadvantageously assessed at regular intervals before, during and/or aftera course of treatment in accordance with the invention, so that changestherein may be detected, e.g. the slowing or halting of cognitivedecline. A variety of neuropsychological tests are known in the art forthis purpose, such as the Mini-Mental State Examination (MMSE) withnorms adjusted for age and education (Folstein et al., J. Psych. Res.,12 (1975), 196-198, Anthony et al., Psychological Med., 12 (1982),397408; Cockrell et al., Psychopharmacology, 24 (1988), 689-692; Crum etal., J. Am. Med. Assoc'n. 18 (1993), 2386-2391). The MMSE is a brief,quantitative measure of cognitive status in adults. It can be used toscreen for cognitive decline or impairment, to estimate the severity ofcognitive decline or impairment at a given point in time, to follow thecourse of cognitive changes in an individual over time, and to documentan individual's response to treatment. Another suitable test is theAlzheimer Disease Assessment Scale (ADAS), in particular the cognitiveelement thereof (ADAS-cog) (See Rosen et al., Am. J Psychiatry, 141(1984), 1356-64).

The invention further provides a kit comprising a first medicamentcomprising a GHS and a second medicament comprising an amyloid modifiertogether with instructions for administering said medicamentssequentially or simultaneously to a patient suffering from AD,age-related cognitive decline, MCL cerebral amyloid angiopathy,multi-infarct dementia, dementia pugilistica or Down syndrome.

The GHS used in the invention may be any compound which has the propertyof stimulating or enhancing secretion of endogenous growth hormone whenadministered to a subject, for example any of the compounds disclosed inthe patents and patent applications listed above. However, preference isgiven to compounds which are suitable for oral administration.

A first class of GHSs suitable for use in the invention is thatdisclosed in WO 94/13696, in particular the subset thereof disclosed inEP 0615977B, the disclosure of which is incorporated herein byreference. Preferred examples of GHSs within this class include thecompound of formula I:

named asN-[1(R)-[(1,2-dihydro-1-methanesulfonylspiro[3H-indole-3,4′-piperidin]-1′-yl)carbonyl]-2-(phenylmethyloxy)ethyl]-2-amino-2-methylpropanamide,and pharmaceutically acceptable salts thereof, in particular themethanesulfonate salt thereof, which may be prepared as described inU.S. Pat. No. 5,767,124.

A second class of GHSs suitable for use in the invention is thatdisclosed in U.S. Pat. No. 5,578,593, the disclosure of which isincorporated herein by reference. Preferred example of GHSs within thisclass include the compound of formula II:

and pharmaceutically acceptable salts thereof, which may be prepared asdescribed in U.S. Pat. No. 5,578,593.

A third class of GHSs suitable for use in the invention is thatdisclosed in WO 92/16524, the disclosure of which is incorporated hereinby reference. Preferred example of GHSs within this class include thecompounds of formulae III and IV:

and pharmaceutically acceptable salts thereof, in particular thetrifluoroacetate salts thereof, which may be prepared as described in WO92/16524.

A fourth class of GHSs suitable for use in the invention is thatdisclosed in WO 97/23508, the disclosure of which is incorporated hereinby reference. Preferred examples of GHSs within this class include thecompound of formula V, also known as NN703:

and pharmaceutically acceptable salts thereof, which may be prepared asdescribed in WO 99/64456.

A fifth class of GHSs suitable for use in the invention is thatdisclosed in WO 97/24369, the disclosure of which is incorporated hereinby reference. Preferred examples of GHSs within this class include thecompound of formula VI:

named as2-amino-N-[2-(3a-(R)-benzyl-2-methyl-3-oxo-2,3,3a,4,6,7-hexahydro-pyrazolo[4,3-c]pyridin-5-yl)-1-(R)-benzyloxymethyl-2-oxo-ethyl]-isobutyramide,and pharmaceutically acceptable salts thereof, in particular theL-tartrate salt, also known as capromorelin, which maybe prepared asdescribed in WO 97/24369 and in Carpino et al, Bioorg. Med. Chem., 11(2003), 581-90.

A sixth class of GHSs suitable for use in the invention is thatdisclosed in WO 98/58947, the disclosure of which is incorporated hereinby reference. Preferred examples of GHSs within this class include thecompound of formula VII:

and pharmaceutically acceptable salts thereof, which may be prepared asdescribed in WO 98/58947.

A seventh class of GHSs suitable for use in the invention is thatdisclosed in WO 99/08699, the disclosure of which is incorporated hereinby reference. Preferred examples of GHSs within this class include thecompound of formula VIII:

and pharmaceutically acceptable salts thereof, which may be prepared asdescribed in WO 99/08699 and WO 02/32878.

Further GHSs suitable for use in the invention include the compound offormula IX;

and pharmaceutically acceptable salts thereof, which may be prepared asdescribed in De Vita et al, J. Med. Chem., 41 (1998), 1716-28, and thecompound of formula X:

and pharmaceutically acceptable salts thereof, which may be prepared asdescribed in Yang et al, J. Med. Chem., 41 (1998), 2439-41.

Preferably, the GHS is selected from the compounds of formulae I, II, V,VI, VII and IX depicted above, and their pharmaceutically acceptablesalts. Most preferably, the GHS used in the invention is themethanesulfonate salt of the compound of formula I which is in one ofthe polymorphic forms described in U.S. Pat. No. 5,767,124.

In one embodiment of the invention, the amyloid modifier is a compoundwhich inhibits the secretion of Aβ, for example an inhibitor of ofγ-secretase (such as those disclosed in WO 01/53255, WO 01/66564, WO01/70677, WO 01/90084, WO 01/7144, WO 02/30912, WO 02/36555, WO02/081435, WO 02/081433, WO 03/018543, WO 03/013506, WO 03/013527, WO03/014075, WO 03/093252, WO 2004/03437, WO 2004/031138 and WO2004/031139, WO 2004/039800 and WO 2004/039370), or a β-secretaseinhibitor (such as those disclosed in WO 03/037325, WO 03/030886, WO03/006013, WO 03/006021, WO 03/006423, WO 03/006453, WO 02/002122, WO01/70672, WO 02/02505, WO 02/02506, WO 02/02512, WO 02/02520, WO02/098849 and WO 02/100820), or any other compound which inhibits theformation or release of Aβ including those disclosed in WO 98/28268, WO02/47671, WO 99/67221, WO 01/34639, WO 01/34571, WO 00/07995, WO00/38618, WO 01/92235, WO 01/77086, WO 01/74784, WO 01/74796, WO01/74783, WO 01/60826, WO 01/19797, WO 01/27108, WO 01/27091, WO00/50391, WO 02/057252, US 2002/0025955 and US2002/0022621, and alsoincluding GSK-3 inhibitors, particularly GSK-3α inhibitors, such aslithium, as disclosed in Phiel et al, Nature, 423 (2003), 435-9.

Within this embodiment, the amyloid modifier is advantageously aγ-secretase inhibitor, preferred examples of which include a compound offormula XI:

wherein:

-   -   m is 0 or 1;    -   Z represents halogen, CN, NO₂, N₃, CF₃, OR^(2a), N(R^(2a))₂,        CO₂R^(2a), OCOR^(2a), COR^(2a), CON(R^(2a))₂, OCON(R^(2a))₂,        CONR^(2a)(OR^(2a)), CON(R^(2a))N(R^(2a))₂, CONHC(═NOH)R^(2a),        heterocyclyl, phenyl or heteroaryl, said heterocyclyl, phenyl or        heteroaryl bearing 0-3 substituents selected from halogen, CN,        NO₂, CF₃, OR^(2a), N(R^(2a))₂, COR^(2a), COR^(2a), CON(R^(2a))₂        and C₁₋₄alkyl;    -   R^(1b) represents H, C₁₋₄alkyl or OH;    -   R^(1c) represents H or C₁₋₄alkyl;    -   with the proviso that when m is 1, R^(1b) and R^(1c) do not both        represent C₁₋₄alkyl;    -   Ar¹ represents C₆₋₁₀aryl or heteroaryl, either of which bears        0-3 substituents independently selected from halogen, CN, NO₂,        CF₃, OH, OCF₃, C₁₋₄alkoxy or C₁₋₄alkyl which optionally bears a        substituent selected from halogen, CN, NO₂, CF₃, OH and        C₁₋₄alkoxy;    -   Ar² represents C₆₋₁₀aryl or heteroaryl, either of which bears        0-3 substituents independently selected from halogen, CN, NO₂,        CF₃, OH, OCF₃, C₁₋₄alkoxy or C₁₋₄alkyl which optionally bears a        substituent selected from halogen, CN, NO₂, CF₃, OH and        C₁₋₄alkoxy;    -   R^(2a) represents H, C₁₋₆alkyl, C₃₋₆cycloalkyl,        C₃₋₆cycloalkylC₁₋₆alkyl, C₂₋₆alkenyl, any of which optionally        bears a substituent selected from halogen, CN, NO₂, CF₃,        OR^(2b), CO₂R^(2b), N(R^(2b))₂, CON(R^(2b))₂, Ar and COAr; or        R^(2a) represents Ar; or two R^(2a) groups together with a        nitrogen atom to which they are mutually attached may complete        an N-heterocyclyl group bearing 0-4 substituents independently        selected from ═O, ═S, halogen, C₁₋₄alkyl, CN, NO₂, CF₃, OH,        C₁₋₄alkoxy, C₁₋₄alkoxycarbonyl, CO₂H, amino, C₁₋₄alkylamino,        di(C₁₋₄alkyl)amino, carbamoyl, Ar and COAr;    -   R^(2b) represents H, C₁₋₆alkyl, C₃₋₆cycloallyl,        C₃₋₆cycloalkylC₁₋₆allyl, C₂₋₆alkenyl, any of which optionally        bears a substituent selected from halogen, CN, NO₂, CF₃, OH,        C₁₋₄alkoxy, C₁₋₄alkoxycarbonyl, CO₂H, amino, C₁₋₄allylamino,        di(C₁₋₄akyl)amino, carbamoyl, Ar and COAr; or R^(2b) represents        Ar; or two R^(2b) groups together with a nitrogen atom to which        they are mutually attached may complete an N-heterocyclyl group        bearing 0-4 substituents independently selected from ═O, ═S,        halogen, C₁₋₄alkyl, CN, NO₂, CF₃, OH, C₁₋₄alkoxy,        C₁₋₄alkoxycarbonyl, CO₂H, amino, C₁₋₄alkylamino,        di(C₁₋₄alkyl)amino, carbamoyl, Ar and COAr;    -   Ar represents phenyl or heteroaryl bearing 0-3 substituents        selected from halogen, C₁₋₄alkyl, CN, NO₂, CF₃, OH, C₁₋₄alkoxy,        C₁₋₄alkoxycabonyl, amino, C₁₋₄alkylamino, di(C₁₋₄alkyl)amino,        carbamoyl, C₁₋₄allylcarbamoyl and di(C₁₋₄alkyl)carbamoyl;    -   “heterocyclyl” at every occurrence thereof means a cyclic or        polycyclic system of up to 10 ring atoms selected from C, N, O        and S, wherein none of the constituent rings is aromatic and        wherein at least one ring atom is other than C; and    -   “heteroaryl” at every occurrence thereof means a cyclic or        polycyclic system of up to 10 ring atoms selected from C, N, O        and S, wherein at least one of the constituent rings is aromatic        and wherein at least one ring atom of said aromatic ring is        other than C;    -   or a pharmaceutically acceptable salt thereof.

Such compounds may be prepared as described in WO 03/018543. Preferredexamples include those defined by formula XIa:

and the pharmaceutically acceptable salts thereof, wherein m is 0 or 1,X is Cl or CF₃, and Y is OH, OC₁₋₆alkyl, NH₂ or NHC₁₋₆alkyl. Particularexamples include those in which m is 1 and Y is OH (or the sodium saltsthereof), and those in which m is 0 and Y is NH₂ or NHC₁₋₆alkyl.

Another preferred class of γ-secretase inhibitors for use in thisembodiment of the invention is that defined by formula XII:

wherein X is a bivalent pyrazole, imidazole, triazole, oxazole,isoxazole, thiazole, isothiazole, thiadiazole or 1,3,4-oxadiazoleresidue optionally bearing a hydrocarbon substituent comprising 1-5carbon atoms which is optionally substituted with up to 3 halogen atoms;and

-   -   R is selected from:

(i) CF₃ or a non-aromatic hydrocarbon group of up to 10 carbon atoms,optionally substituted with halogen, CF₃, CHF₂, CN, OH, CO₂H, C₂₋₆acyl,C₁₋₄alkoxy or C₁₋₄alkoxycarbonyl;

(ii) a non-aromatic heterocyclic group comprising up to 7 ring atoms ofwhich up to 3 are chosen from N, O and S and the remainder are carbon,bearing 0-3 substituents independently selected from oxo, halogen, CN,C₁₋₆alkyl, OH, CF₃, CHF₂, CH₂F, C₂₋₆acyl, CO₂H, C₁₋₄alkoxy andC₁₋₄alkoxycarbonyl;

(iii) phenyl or 6-membered heteroaryl, either of which bears 0-3substituents independently selected from halogen, CF₃, CHF₂, CH₂F, NO₂,CN, OCF₃, C₁₋₆alkyl and C₁₋₆alkoxy; and

(iv) N(R^(a))₂ where each R^(a) independently represents H or C₁₋₆alkylwhich is optionally substituted with halogen, CF₃, CHF₂, CN, OH, CO₂H,C₂ ₆acyl, C₁₋₄alkoxy or C₁₋₄alkoxycarbonyl;

or a pharmaceutically acceptable salt thereof.

X is very aptly 5-substituted-thiazol-2-yl,5-substituted-4-methylthiazol-2-yl, 5-substituted-1-methylpyrazol-3-yl,1-substituted-imidazol-4-yl or 1-substituted-1,2,4-triazol-3-yl.Preferably, R represents optionally-substituted phenyl or heteroarylsuch as phenyl, monohalophenyl, dihalophenyl, trihalophenyl,cyanophenyl, methylphenyl, methoxyphenyl, trifluoromethylphenyl,trifluoromethylphenyl, pyridyl, monohalopyridyl andtrifluoromethylpyridyl, wherein “halo” refers to fluoro or chloro.Particularly preferred identities of R—X— include5-(4-fluorophenyl)-1-methylpyrazol-3-yl,5-(4-chlorophenyl)-1-methylpyrazol-3-yl and1-(4-fluorophenyl)imidazol-4-yl. Such compounds may be prepared bymethods disclosed in WO 03/093252.

Another preferred class of γ-secretase inhibitors for use in thisembodiment of the invention is that defined by formula XIII:

wherein the pyrazole group is attached at one of the positions indicatedby an asterisk and X is attached at a position adjacent thereto;

-   -   X represents H, OH, C₁₋₄alkoxy, Cl or F;    -   Ar represents phenyl or 6-membered heteroaryl, either of which        bears 0-3 substituents independently selected from halogen, CF₃,        CHF₂, CH₂F, NO₂, CN, OCF₃, C₁₋₆alkyl and C₁₋₆alkoxy;    -   R¹ represents a hydrocarbon group of 1-5 carbon atoms which is        optionally substituted with up to 3 halogen atoms; and    -   R² represents H or a hydrocarbon group of 1-10 carbon atoms        which is optionally substituted with up to 3 halogen atoms;    -   provided that when X is H, R² does not represent        2,2,2-trifluoroethyl;        or a pharmaceutically acceptable salt thereof.

Preferred examples of compounds of formula XIII include those in whichAr is 4-fluorophenyl, R¹ is methyl, X is H and R² is benzyl, n-propyl,2,2-dimethylpropyl, n-butyl, isopropyl, t-butyl, 3,3,3-trifluoropropyl,allyl, cyclobutyl or cyclopropylmethyl. Such compounds may be preparedby methods disclosed in WO 2004/039800.

Another preferred class of γ-secretase inhibitors for use in thisembodiment of the invention is that defined by formula XIV:

wherein the pyrazole group is attached at one of the positions indicatedby an asterisk and X is attached at a position adjacent thereto;

-   -   X represents H, OH, C₁₋₄alkoxy, Cl or F;    -   Y represents a bond, O or NR³;    -   Ar represents phenyl or 6-membered heteroaryl, either of which        bears 0-3 substituents independently selected from halogen, CF₃,        CHF₂, CH₂F, NO₂, CN, OCF₃, C₁₋₆alkyl and C₁₋₆alkoxy;    -   R¹ represents a hydrocarbon group of 1-5 carbon atoms which is        optionally substituted with up to 3 halogen atoms; and    -   R² represents a hydrocarbon group of 1-10 carbon atoms which is        optionally substituted with up to 3 halogen atoms, or heteroaryl        of 5 or 6 ring atoms optionally bearing up to 3 substituents        independently selected from halogen, CF3, CHF₂, CH₂F, NO₂, CN,        OCF₃, C₁₋₆alkyl and C₁₋₆alkoxy; or when Y represents NR³, R² and        R³ together may complete a heterocyclic ring of up to 6 members        which optionally bears up to 3 substituents independently        selected from halogen, CF₃, CH2, CH₂F, NO₂, CN, OCF₃, C₁₋₆alkyl        and C₁₋₆alkoxy;    -   R³ represents H or C₁₋₄alkyl, or together with R² completes a        heterocyclic ring as defined above;        or a pharmaceutically acceptable salt thereof.

Preferred examples of compounds of formula XIV include those in which Aris 4-fluorophenyl, R¹ is methyl, X is H, and either Y is a bond and R²is n-butyl, 4-fluorophenyl, 5-chloro-2-thienyl, 5-isothiazolyl,6-chloropyridin-3-yl or 2-thienyl, or Y is NR³ and NR²R³ iscyclobutylamino, 2,2,2-trifluoroethylamino, n-propylamino,N-methyl-n-propylamino, dimethylamino, pyrrolidin-1-yl or4-(trifluoromethyl)piperidin-1-yl. Such compounds maybe prepared asdescribed in WO 2004/039370.

Another preferred class of γ-secretase inhibitors for use in thisembodiment of the invention is that defined by formula XV:

wherein n is 1 or 2;

-   -   R¹ represents CF₃ or C₁₋₆alkyl, C₂₋₆alkenyl, C₃₋₉cycloalkyl or        C₃₋₆cycloalkylC₁₋₆alkyl, any of which may bear up to 2        substituents selected from halogen, CN, CF₃, OR³, COR³, CO₂R³,        OCOR⁴, SO₂R⁴, N(R⁵)₂, and CON(⁵)₂,    -   or R¹ represents aryl, arylC₁₋₆allyl, C-heterocyclyl or        C-heterocyclylC₁₋₆alyl;    -   R² represents H or C₁₋₄alkyl;    -   R³ represents H, C₁₋₄alkyl, phenyl or heteroaryl;    -   R⁴ represents C₁₋₄alkyl, phenyl or heteroaryl;    -   R⁵ represents H or C₁₋₄alkyl, or two R⁵ groups together with a        nitrogen atom to which they are mutually attached complete an        azetidine, pyrrolidine, piperidine, morpholine, thiomorpholine        or thiomorpholine-1,1-dioxide ring;    -   Ar¹ and Ar² independently represent phenyl or heteroaryl, either        of which bears 0-3 substituents independently selected from        halogen, CN, NO₂, CF₃, CHF₂, OH, OCF₃, CHO, CH═NOH, C₁₋₄alkoxy,        C₁₋₄alkoxycarbonyl, C₂₋₆acyl, C₂₋₆alkenyl and C₁₋₄alkyl which        optionally bears a substituent selected from halogen, CN, NO₂,        CF₃, OH and C₁₋₄alkoxy;    -   “aryl” at every occurrence thereof refers to phenyl or        heteroaryl which optionally bear up to 3 substituents selected        from halogen, CN, NO₂, CF₃, OCF₃, OR³, COR³, CO₂R³, OCOR⁴,        N(⁵)₂, CON(⁵)₂ and optionally-substituted C₁₋₆allyl, C₁₋₆alkoxy,        C₂₋₆alkenyl or C₂₋₆alkenyloxy wherein the substituent is        selected from halogen, CN, CF₃, phenyl, OR³, CO₂R³, OCOR⁴,        N(R⁵)₂ and CON(F⁵)₂; and    -   “C-heterocyclyl” and “N-heterocyclyl” at every occurrence        thereof refer respectively to a heterocyclic ring system bonded        through carbon or nitrogen, said ring system being non-aromatic        and comprising up to 10 atoms, at least one of which is O, N or        S, and optionally bearing up to 3 substituents selected from        oxo, halogen, CN, NO₂, CF₃, OCF₃, OR³, COR³, CO₂R³, OCOR⁴,        OSO₂R⁴, N(R⁵)₂, CON(R⁵)₂ and optionally-substituted phenyl,        C₁₋₆alkyl, C₁₋₆alkoxy, C₂₋₆alkenyl or C₂₋₆alkenyloxy wherein the        substituent is selected from halogen, CN, CF₃, OR³, CO₂R³,        OCOR⁴, N(R⁵)₂ and CON(R⁵)₂;    -   or a pharmaceutically acceptable salt thereof.

Preferred examples of compounds of formula XV include those in which R¹is CF₃, Ar² is 2,5-difluorophenyl and Ar¹ is 4-chlorophenyl,4-trifluoromethylphenyl or 6-trifluoromethylpyridin-3-yl. Compounds offormula XV may be prepared as described in WO 2004/031139.

In a second embodiment of the invention, the amyloid modifier is acompound which selectively inhibits secretion of the 1-42 isoform of Aβ.Suitable examples of such compounds include the non-steroidalantiinflammatory drugs (NSAIDs) and their analogues disclosed in WO01/78721 and US 2002/0128319, such as sulindac sulfide, flufenamic acid,ibuprofen, flurbiprofen, fenoprofen, mefenamic acid, indomethacin and(R)-flurbiprofen. A preferred example is (R)-flurbiprofen.Alternatively, an NSAID derivative capable of releasing nitric oxide maybe employed (e.g. compounds as disclosed in WO 02/092072 and in Jantzenet al, J. Neuroscience, 22 (2002), 226-54). Preferred examples ofNO-releasing compounds include the 4-nitrooxybutyl ester of flurbiprofen(made by NiCox and also known as HCT-1026) and the compound:

known as NCX-2216 (NiCox). As a further alternative within thisembodiment, a compound which modulates the activity of PPARα and/orPPARδ (as disclosed in WO 02/100836) maybe employed.

In a third embodiment of the invention, the amyloid modifier is acompound which inhibits the aggregation of Aβ. Suitable examples includechelating agents such as clioquinol (Gouras and Beal, Neuron, 30 (2001),641-2) and the compounds disclosed in WO 99/16741, in particular thatknown as DP-109 (Kalendarev et al, J. Pharm. Biomed. Anal., 24 (2001),967-75). Other inhibitors of Aβ aggregation suitable for use in theinvention include the compounds disclosed in WO 96/28471, WO 98/08868and WO 00/052048, including the compound known as Apan™ (Praecis); WO00/064420, WO 03/017994, WO 99/59571 and the compound known as Alzhemed™(Neurochem); WO 00/149281 and the compositions known as PTI-777 andPTI-00703 (ProteoTech); WO 96/39834, WO 01/83425, WO 01/55093, WO00/76988, WO 00/76987, WO 00/76969, WO 00/76489, WO 97/26919, WO97/16194, and WO 97/16191.

In a fourth embodiment of the invention, the amyloid modifier is anantibody which binds selectively to Aβ. Said antibody may be polyclonalor monoclonal, but is preferably monoclonal, and is preferably human orhumanized. Preferably, the antibody is capable of sequestering solubleAβ from biological fluids, as described in WO 03/016466, WO 03/016467,WO 03/015691 and WO 01/62801. Suitable antibodies include humanizedantibody 266 (described in WO 01/62801) and the modified version thereofdescribed in WO 03/016466. Further suitable antibodies include thosespecific to ADDLS as described in WO 2004/031400.

In a particular embodiment of the invention, the amyloid modifier isselected from:

(a) compounds which inhibit the secretion of Aβ;

(b) compounds which selectively inhibit the secretion of the 1-42isoform of Aβ;

(c) compounds which inhibit the aggregation of Aβ.

Depending on whether they are to be administered together or separately,the GHS and amyloid modifier are typically supplied as single ormultiple pharmaceutical compositions comprising the active species and apharmaceutically acceptable carrier. Preferably these compositions arein unit dosage forms such as tablets, pills, capsules, powders,granules, sterile parenteral solutions or suspensions, metered aerosolor liquid sprays, drops, ampoules, transdermal patches, auto-injectordevices or suppositories; for oral, parenteral, intranasal, sublingualor rectal administration, or for administration by inhalation orinsufflation. The principal active ingredient typically is mixed with apharmaceutical carrier, e.g. conventional tableting ingredients such ascorn starch, lactose, sucrose, sorbitol, talc, stearic acid, magnesiumstearate and dicalcium phosphate, or gums, dispersing agents, suspendingagents or surfactants such as sorbitan monooleate and poly(ethyleneglycol), and other pharmaceutical diluents, e.g. water, to form ahomogeneous preformulation composition containing one or both activespecies, or pharmaceutically acceptable salts thereof. When referring tothese preformulation compositions as homogeneous, it is meant that theactive species is or are dispersed evenly throughout the composition sothat the composition may be readily subdivided into equally effectiveunit dosage forms such as tablets, pills and capsules. Thispreformulation composition is then subdivided into unit dosage forms ofthe type described above, generally containing from 0.01 to about 500 mgof the active species. Typical unit dosage forms contain from 0.05 to100 mg, for example 0.05, 0.1, 0.5, 1, 2, 5, 10, 25, 50 or 100 mg, ofthe active species. Tablets or pills of the pharmaceuticalcomposition(s) can be coated or otherwise compounded to provide a dosageform affording the advantage of prolonged action. For example, thetablet or pill can comprise an inner dosage and an outer dosagecomponent, the latter being in the form of an envelope over the former.The two components can be separated by an enteric layer which serves toresist disintegration in the stomach and permits the inner component topass intact into the duodenum or to be delayed in release. A variety ofmaterials can be used for such enteric layers or coatings, suchmaterials including a number of polymeric acids and mixtures ofpolymeric acids with such materials as shellac, cetyl alcohol andcellulose acetate.

The liquid forms in which the pharmaceutical compositions useful in thepresent invention may be incorporated for administration orally or byinjection include aqueous solutions, liquid- or gel-filled capsules,suitably flavoured syrups, aqueous or oil suspensions, and flavouredemulsions with edible oils such as cottonseed oil, sesame oil, coconutoil or peanut oil, as well as elixirs and similar pharmaceuticalvehicles. Suitable dispersing or suspending agents for aqueoussuspensions include synthetic and natural gums such as tragacanth,acacia, alginate, dextran, sodium carboxymethylcellulose,methylcellulose, poly(ethylene glycol), poly(vinylpyrrolidone) andgelatin.

Pharmaceutical compositions suitable for oral administration arepreferred, except when the amyloid modifier is an antibody, in whichcase parenteral administration of the antibody is preferred, e.g. bysubcutaneous, intravenous or intraperitoneal injection.

For treatment or prevention of AD, the GHS and amyloid modifier may bedosed at the levels which are effective for the original purposes of theseparate compounds. Thus, the GHS will typically be dosed at levelsknown to provide increased secretion of endogenous growth hormone in ahuman subject, and the amyloid modifier at levels known to causesignificant inhibition of the secretion of Aβ, or of the 1-42 isoformthereof, or significant inhibition of the aggregation of Aβ, orsignificant sequestration of soluble Aβ, as appropriate. In many cases,these dosage levels are available from the published literature, butotherwise are readily determined by standard clinical methods. However,as explained above, it may be possible and advantageous to use a smallerdose of the amyloid modifier than would otherwise be indicated, in viewof the synergistic interaction with the GHS.

The frequency of dosing of the relevant compounds (e.g. once, twice,three times or four times per day) may be selected according to thepharmacokinetic profiles of the compounds concerned.

In the case of the preferred GHS of formula I, doses of about 0.01 to5.0 mg/kg per day, preferably about 0.05 to 2.5 mg/kg per day, morepreferably about 0.1 to 1.0 mg/kg of body weight per day, may becontemplated. In particular, a dose equivalent to 5 mg, 10 mg or 25 mgof the free base may be administered orally once daily to a patient.

In the case of a compound which inhibits the secretion of Aβ, the dosagemay be adjusted so as to provide complete suppression of the secretionof Aβ, or only partial suppression thereof, for example a 50% reductionin Aβ secretion. In the case of a γ-secretase inhibitor of formula XI orXII above, daily oral doses of about 25 to 500 mg per person arecontemplated, in particular about 25 to 250 mg per person.

In a further aspect, the invention provides a pharmaceutical compositioncomprising, in a pharmaceutically acceptable carrier, a compound offormula I or a pharmaceutically acceptable salt thereof and a compoundof formula XI(a) or a pharmaceutically acceptable salt thereof.Preferably the compound of formula I is in the form of themethanesulfonate salt. Preferably, the pharmaceutical composition is ina unit dose form suitable for oral administration, such as a tablet or acapsule. In a particular embodiment, said unit dose form contains theequivalent of 5, 10 or 25 mg of the free base of formula I and theequivalent of from 25 to 250 mg of the compound of formula XI(a).

1-13. (canceled)
 14. A method of treatment or prevention of a diseaseassociated with deposition of Aβ in the brain comprising administeringto a patient in need thereof a therapeutically effective amount of agrowth hormone secretagogue in combination with a therapeuticallyeffective amount of at least one agent which modifies the production orprocessing of Aβ in the brain, said agent being selected from: (a)compounds which inhibit the secretion of Aβ; (b) compounds whichselectively inhibit the secretion of the 1-42 isoform of Aβ; (c)compounds which inhibit the aggregation of Aβ; and (d) antibodies whichselectively bind to Aβ.
 15. The method of claim 14 wherein the diseaseis Alzheimer's disease.
 16. The method of claim 15 wherein the patientsuffers from mild cognitive impairment.
 17. The method of claim 16wherein the patient additionally possesses one or more risk factors fordeveloping Alzheimer's disease selected from: a family history of thedisease; a genetic predisposition to the disease; elevated serumcholesterol; adult-onset diabetes mellitus; elevated baselinehippocampal volume; elevated CSF levels of total tau; elevated CSFlevels of phospho-tau; and lowered CSF levels of Aβ(1-42).
 18. Themethod of claim 14 wherein the growth hormone secretagogue isN-[1(R)-[(1,2-dihydro-1-methanesulfonylspiro[3H-indole-3,4′-piperidin]-1′-yl)carbonyl]-2-(phenylmethyloxy)ethyl]-2-amino-2-methylpropanamide,or pharmaceutically acceptable salt thereof.
 19. The method of claim 14wherein the amyloid modifier is a γ-secretase inhibitor.
 20. The methodof claim 19 wherein the γ-secretase inhibitor is a compound of formulaXIa:

and the pharmaceutically acceptable salts thereof, wherein m is 0 or 1,X is Cl or CF₃, and Y is OH, OC₁₋₆alkyl, NH₂ or NHC₁₋₆alkyl.
 21. Themethod of claim 14 wherein the amyloid modifier is a compound whichselectively inhibits the secretion of the 1-42 isoform of Aβ.
 22. Themethod of claim 21 wherein the amyloid modifier is R-flurbiprofen.
 23. Apharmaceutical composition comprising in a pharmaceutically acceptablecarrier, a growth hormone secretagogue and an amyloid modifier selectedfrom: (a) compounds which inhibit the secretion of Aβ; (b) compoundswhich selectively inhibit the secretion of the 1-42 isoform of Aβ; and(c) compounds which inhibit the aggregation of Aβ.